In the discussion of the background that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art.
Within the field of chip removing or cutting machining of, above all, blanks of metal, a continuous development is going on with the purpose of making more effective not only the capacity of the tools to carry out the machining in a fast and accurate way, but also the manufacture of the different parts of the tools in the form of basic bodies (holders) and replaceable cutting inserts. A trend is to reduce the costs of the manufacture of the tools. This has, among other things, led to cutting inserts manufactured from cemented carbide or the like, which are most common on the market, in connection with compression-moulding and sintering having obtained a better and better dimensional accuracy. In order to obtain a good precision of the cutting inserts, previously it was necessary to subject the same to expensive grinding operations, but with the improved compression-moulding and sintering technique, it has become possible to use direct-pressed, i.e., unground, cutting inserts in more and more applications. However, the development has not progressed further than that the tool designer still has to allow for a dimensional variation in the order of ±0.5% of the nominal dimensions of the cutting inserts.
Older cutting tools of the type equipped with replaceable and indexable cutting inserts were designed with fairly simple means for fixing the cutting insert in the basic body of the tool. More precisely, the basic body was formed with a so-called insert seat, which was delimited by a plane bottom surface and two plane side support surfaces, orientated at an angle to each other, against which plane contact surfaces of the cutting insert were urged, usually by means of a screw or a clamp. In order to give an acceptable machining precision, said cutting inserts had to be subjected to expensive grinding along the contact surfaces thereof.
Recently have, among other things as a consequence of the improved insert manufacturing technique, tools been developed, the interfaces of which between the basic body and the cutting insert are formed with connecting surfaces that individually include male-like as well as female-like engagement means engaging each other. Originally, said connecting surfaces consisted of simple, so-called serration connecting surfaces of the type that includes a plurality of parallel, male-like ridges and female-like grooves, the ridges of which in one of the connecting surfaces engage the grooves in the other connecting surface, and vice versa. A dominant angle between the pairs of flanks of the ridges and grooves in such connecting surfaces was 60°. In the next stage of development, said interfaces were refined by the fact that certain ridges were orientated at right or other angles to the other ridges, often in combination with the number of ridges and grooves being reduced to a minimum. Such so-called cross serration surfaces have the advantage of locking the cutting insert in two coordinate directions instead of only one, as was the case with the simple, parallel ridges.
During the development up to today's modern interfaces, which make use of crosswise acting male and female members in the form of, e.g., ridges and grooves, the flank angles of the members have increased from the fairly acute 60° up to 90° and even more. The object hereof has, among other things, been to facilitate the possibilities of accommodating possible, small form defects of the cutting insert without jeopardizing the positioning of the cutting edges in relation to the basic body. Characteristic of the modern interfaces is furthermore that all flanks of the engagement means included in the connecting surface of the cutting insert are essentially situated in a common basal plane along the underside of the cutting insert, in the same way as all flanks of the engagement means included in the connecting surface of the basic body are essentially situated in a common bottom plane (which coincides with the basal plane of the cutting insert, when the cutting insert is mounted in the basic body).
Examples of cutting tools having later times' interfaces are disclosed in for instance: U.S. Pat. No. 3,629,919, U.S. Pat. No. 5,810,518, U.S. Pat. No. 5,931,613, U.S. Pat. No. 6,146,060, SE 9702500-1, and SE 0101752-4.
Many known tools having the modern type of interface between the cutting insert and basic body work in a meritorious way in certain applications, but insufficiently in others. Thus, it has turned out that cutting inserts, which work under severe conditions and are subjected to cutting forces that are dominating in one direction but not in others, run the risk of being dislodged from the positions thereof. This is in particular the case in milling, where the milling or cutting insert is subjected to considerable radial forces, but moderate axial forces. More precisely, milling is an intermittent machining during which the cutting insert, each time it impinges on or engages the workpiece, is subjected to extreme, instantaneous radial forces that aim to displace and turn the same, and in such a way deform the flanks included in the primary connecting surface of the basic body. In addition, the cutting insert tends to lift at the rear edge.